Purpose:
Migration Server A for all accounts and mail (include password,user settings,aliases,distribution lists,And so on.) to the server B
All is not changed,Just replace ther Server A, What do i do?
Any suggestions?

It covers a server move from one platform to another. Using rsync while the server was running, and then rsync once again while neither server was running minimized the downtime to half an hour or so. This was for a 900 or so user system with 350GB of disk usage so YMMV.